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arXiv 1903.04050astro-ph.SR
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耀斑爆发前和爆发期间太阳活动区的电流

Solar Active Region Electric Currents Before and During Eruptive Flares

Brigitte Schmieder, Guillaume Aulanier

摘要:

“爆发耀斑之前和期间的太阳活动区电流”一章利用太阳观测资料、依赖于这些观测资料的非线性无力场外推以及三维磁流体动力学(MHD)模型,讨论了太阳磁结构爆发前状态和爆发过程中的电流。讨论解决了中性与非中性电流在活动区的问题,并得出结论,MHD模型能够解释非中性电流在活动区的极性反转线沿强磁剪切的存在,从而证实了以前的观察已经包含这一结果。这些模型还捕捉到了太阳爆发期间活动区电流行为的本质,分别预测了耀斑带内部和膨胀通量绳内部的电流密度增加和减少。从矢量磁场观测中推断出的光球电流密度图显示出与MHD模型结果相似的旋转带状图案,这被解释为活动区磁系统之间的磁绳和准分界线层(QSL)的签名。在这些QSL的总电流的增强在喷发和喷发通量绳的脚点电流密度下降,已被证实的观测。

英文摘要:

The chapter "Solar Active Region Electric Currents Before and During Eruptive Flares" is a discussion on electric currents in the pre-eruption state and in the course of eruptions of solar magnetic structures, using information from solar observations, nonlinear force-free field extrapolations relying on these observations, and three-dimensional magnetohydrodynamic (MHD) models. The discussion addresses the issue of neutralized vs. non-neutralized currents in active regions and concludes that MHD models are able to explain non-neutralized currents in active regions by the existence of strong magnetic shear along the polarity inversion lines, thus confirming previous observations that already contained this result. The models have also captured the essence of the behavior of electric currents in active regions during solar eruptions, predicting current-density increases and decreases inside flare ribbons and in the interior of expanding flux ropes respectively. The observed photospheric current density maps, inferred from vector magnetic field observations, exhibit similar whirling ribbon patterns to the MHD model results, that are interpreted as the signatures of flux ropes and of quasi-separatrix layers (QSLs) between the magnetic systems in active regions. Enhancement of the total current in these QSLs during the eruptions and decreasing current densities at the footpoint of erupting flux ropes, has been confirmed in the observations.

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